Near field communication (NFC) is one type of radio frequency identification (RFID) technology through which various wireless data is transmitted and received within a short distance of about 10 cm and is a non-contact communication technology using a frequency band of 13.56 MHz. Since a communication distance of the NFC is short, security is relatively high, and a cost is cheap, and thus the NFC is spotlighted as a short distance communication technology. Since data may be read and written using the NFC, there is an advantage in that a dongle (reader) needed for using a conventional RFID is not necessary.
Meanwhile, a technology for converting electrical energy into an electromagnetic wave capable of being wirelessly transmitted and transmitting the electromagnetic wave is referred to as a wireless power transmission or wireless power charge (WPC) technology, and the WPC technology is divided into an electromagnetic induction type WPC technology, a magnetic resonance type WPC technology, and the like according to an implementation method, and the electromagnetic induction type WPC technology has already been commercialized and standardized.
Specifically, the electromagnetic induction type WPC is operated according to a principle in which a current is applied to a power transmission coil to induce a magnetic field, and the magnetic field which is changed depending on time induces the power transmission coil to generate a current again to supply electric charges to a battery connected to the power transmission coil. The WPC technology has a very high power transmission efficiency of 90% or more, is not harmful to a human body, and may be widely applied to any technology from a device which needs small amounts of power, such as a smartphone, to a device which needs large amounts of power such as an electric vehicle.
In addition, a magnetic secure transmission (MST) technology recently becoming an issue with regards to credit card linked payment of a smartphone is a technology in which, when a mobile device having credit card information is moved adjacent to a credit card payment terminal, the terminal may automatically read the credit card information and payment may be performed. Since payment is performed by wirelessly transmitting the information of the magnetic credit card, the MST technology has an advantage of not using the above-described NFC technology.
Electromagnetic waves (or radiation noise) generated by electronic devices having functions, such as a variety of wireless communications, power transmission and reception, data transmission and reception, and the like described above, may have negative influences in which malfunctions of peripheral electronic devices occur and health of a user is damaged when a human body is exposed to the electromagnetic waves. Accordingly, in order to shield an electromagnetic wave generated by an electronic device and suppress an eddy current, an electromagnetic wave shielding sheet formed of magnetic materials, such as a ferrite, is mounted on and used in an antenna module.
A shield cap is formed above a circuit module installed in a mobile communication terminal, and when an electromagnetic wave shield body is formed by forming a ferrite sheet composite body on the shield cap, an electromagnetic wave generated by the circuit module may be efficiently shielded.
In addition, a magnetization direction of a magnetic material used for NFC, WPC, or MST has to be easily changed according to a phase shaft of an external alternate current electromagnetic field, and a magnetic wave phenomenally distributed in a space has to be moved to an inside of the magnetic material to form a magnetic circuit having a high density magnetic flux so that the magnetic material serves to shield the electromagnetic wave affecting a terminal body or battery.
Here, a magnetic permeability among properties of a magnetic material refers to a ratio of a magnetic flux density generated when the magnetic material is magnetized by being influenced by a magnetic field to a magnitude of a magnetic field in a vacuum, and since the magnetic permeability is an indicator for indicating a level to which a magnetic flux density may be increased, a magnetic material having a high magnetic permeability is required to minimize a magnetic field being leaked.
Furthermore, in mobile devices and the like, as various wireless power/data transmission and reception technologies are developed and include composite functions which are two or more functions, properties such as a magnetic permeability and a saturated magnetization value of a ferrite electromagnetic wave shielding sheet need to be optimized to easily perform corresponding functions.